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Issue 42, 2016
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Oxygen diffusion and surface exchange in the mixed conducting oxides SrTi1−yFeyO3−δ

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Abstract

Oxygen transport in the mixed ionic–electronic conducting perovskite-oxides SrTi1−yFeyO3−δ (with y = 0.5 and y = 1.0) was studied by oxygen isotope exchange measurements. Experiments were performed on thin-film samples that were grown by Pulsed Laser Deposition (PLD) on MgO substrates. Isotope penetration profiles were introduced by 18O2/16O2 exchanges into the plane of the films at various temperatures in the range 773 < T/K < 973 at an oxygen activity aO2 = 0.5. Isotope profiles were determined subsequently by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), and their analysis yielded tracer diffusion coefficients D* and oxygen surface exchange coefficients k*. Activation energies for oxygen diffusion ΔHD* and surface exchange ΔHk* were obtained. Isothermal values of D* and values of ΔHD* are compared with literature data as a function of Fe content. D* is seen to increase monotonically with Fe content; ΔHD* shows more complex behaviour. D* and ΔHD* are also compared with the predictions of defect-chemical models. Analogous comparisons with literature data for k* and ΔHk* indicate, in contrast to prior studies, no mechanistic difference between electron-poor and electron-rich materials. It is concluded that the single operative mechanism of surface exchange for the entire series of STF compositions requires conduction-band electrons (minority electronic charge-carriers).

Graphical abstract: Oxygen diffusion and surface exchange in the mixed conducting oxides SrTi1−yFeyO3−δ

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Publication details

The article was received on 19 Aug 2016, accepted on 08 Oct 2016 and first published on 10 Oct 2016


Article type: Paper
DOI: 10.1039/C6CP05756J
Citation: Phys. Chem. Chem. Phys., 2016,18, 29495-29505
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    Oxygen diffusion and surface exchange in the mixed conducting oxides SrTi1−yFeyO3−δ

    V. Metlenko, W. Jung, S. R. Bishop, H. L. Tuller and R. A. De Souza, Phys. Chem. Chem. Phys., 2016, 18, 29495
    DOI: 10.1039/C6CP05756J

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